1. Field of the Invention
The present invention is related to pneumatic diaphragm valves.
2. State of the Prior Art
There are many uses for valves that open and close in response to some input or inputs, such as electric signals and/or pneumatic actuations. Pneumatic actuations are essentially air switches that are often accomplished by using smaller electric solenoid devices to switch high pressure gas, for example compressed air, on and off to gas actuated larger valves. The gas pressure, for example about 60 to 100 p.s.i.g. (4.1 to 6.9 bar, 0.41 to 0.69 MPa, 0.41 to 0.69 MN/m2), is applied to a valve actuator to open and close one or more valve ports, and the solenoid device or valve turns the high pressure gas to the pneumatic valve actuator on and off. Thus, a small current applied to the solenoid switches a large amount of high pressure gas on and off.
Some uses require valves that are capable of opening and closing very fast as well as to be durable, reliable, and accurate over many open and close cycles and to be resistant to corrosive and highly reactive gases. For example, but not for limitation, in valves used to control flows of precise amounts or measures of reactant gases into semiconductor production reactors, especially for atomic layer deposition (ALD) processes in which precise amounts of reactant gas flows are turned on and off repeatedly and very rapidly through many cycles as thin film layers are grown by one atomic layer or less during every ALD deposition cycle. In such ALD processes, it is desirable for the flow control valves to open and close fast enough to produce virtually digital fully “on” and completely “off” reactant gas flows in high frequency valve cycles or repetitions to maximize the rate of deposition while maintaining precision reactant gas flow control.
Pneumatic diaphragm valves (sometimes also called pilot operated pneumatic valves, pneumatic valves, etc.) are often preferred for many of these kinds of uses, because they are clean, inexpensive, and compact. However, traditional or conventional pneumatic diaphragm valves have had inherent speed limitations and service life deficiencies that limit their usefulness in high speed applications, and the lack of better alternatives has contributed to the difficulty of developing otherwise promising ALD techniques into economical semiconductor fabrication processes on a commercially viable scale. Therefore, improvements have been needed for a number of years to enable pneumatic diaphragm valves to operate effectively at much faster speeds and higher cycle frequencies, which have eluded valve manufacturers prior to this invention.